Legislation in Australia automatically cancels a dual-citizen's citizenship when they engage in terrorism, he said.
"Australia's interest here is that we do not want to see terrorists who fought with terrorism organisations enjoying privileges of citizenship", he said.
"We have continually raised with Australia our view that the decision was wrong", she said.
"The Australian behaviour is despicable on a couple of fronts, not the least of which is the diplomatic front with regards to us".
"Any fair minded person would consider this person an Australian, and that is my view too", Ardern said.
"We will put our hands up when we need to own a situation - we would expect the same from Australia. But now there are two children involved so we have to resolve this issue with those two children in mind".
When asked this morning if New Zealand should block the person's return, National leader Judith Collins said that "most New Zealanders like me, would consider such a person not someone we would go out of our way to assist back to New Zealand. other than meeting the obligations the Government has to".